Mark all required fields for config. Throw if no input_* field specified

- Add custom validator to throw if neither input_filter or
  input_<files|directories> are specified

- Set field expecting paths to type Path

- Now that default_config isn't used in code. We can update
  fields in rawconfig to specify whether they're required or not.
  This lets pydantic validate config file and throw appropriate error

src/utils/rawconfig.py

@@ -3,7 +3,7 @@ from pathlib import Path
 from typing import List, Optional
 
 # External Packages
-from pydantic import BaseModel
+from pydantic import BaseModel, validator
 
 # Internal Packages
 from src.utils.helpers import to_snake_case_from_dash
@@ -14,17 +14,29 @@ class ConfigBase(BaseModel):
         allow_population_by_field_name = True
 
 class TextContentConfig(ConfigBase):
-    compressed_jsonl: Optional[Path]
-    input_files: Optional[List[str]]
+    input_files: Optional[List[Path]]
     input_filter: Optional[str]
-    embeddings_file: Optional[Path]
+    compressed_jsonl: Path
+    embeddings_file: Path
+
+    @validator('input_filter')
+    def input_filter_or_files_required(cls, input_filter, values, **kwargs):
+        if input_filter is None and ('input_files' not in values or values["input_files"] is None):
+            raise ValueError("Either input_filter or input_files required in all content-type.<text_search> section of Khoj config file")
+        return input_filter
 
 class ImageContentConfig(ConfigBase):
-    use_xmp_metadata: Optional[bool]
-    batch_size: Optional[int]
     input_directories: Optional[List[Path]]
     input_filter: Optional[str]
-    embeddings_file: Optional[Path]
+    embeddings_file: Path
+    use_xmp_metadata: bool
+    batch_size: int
+
+    @validator('input_filter')
+    def input_filter_or_directories_required(cls, input_filter, values, **kwargs):
+        if input_filter is None and ('input_directories' not in values or values["input_directories"] is None):
+            raise ValueError("Either input_filter or input_directories required in all content-type.image section of Khoj config file")
+        return input_filter
 
 class ContentConfig(ConfigBase):
     org: Optional[TextContentConfig]
@@ -34,12 +46,12 @@ class ContentConfig(ConfigBase):
     markdown: Optional[TextContentConfig]
 
 class TextSearchConfig(ConfigBase):
-    encoder: Optional[str]
-    cross_encoder: Optional[str]
+    encoder: str
+    cross_encoder: str
     model_directory: Optional[Path]
 
 class ImageSearchConfig(ConfigBase):
-    encoder: Optional[str]
+    encoder: str
     model_directory: Optional[Path]
 
 class SearchConfig(ConfigBase):
@@ -48,8 +60,8 @@ class SearchConfig(ConfigBase):
     image: Optional[ImageSearchConfig]
 
 class ConversationProcessorConfig(ConfigBase):
-    openai_api_key: Optional[str]
-    conversation_logfile: Optional[str]
+    openai_api_key: str
+    conversation_logfile: Path
 
 class ProcessorConfig(ConfigBase):
     conversation: Optional[ConversationProcessorConfig]